X-Ray Investigations of the Low-Temperature Phases of the Organic Metals α- and β-(BEDT-TTF)<sub>2</sub>I<sub>3</sub>

Endres, H.; Keller, Heimo J.; S̀wietlik, R.; Schweitzer, Dieter; Angermund, Klaus

doi:10.1515/zna-1986-1110

Cited by 43 publications

(32 citation statements)

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“…Even very small changes can seriously influence the superconducting transition. In the organic charge transfer-salt /?-(BEDT-TTF) 2 I 3 [BEDT-TTF = bis-(ethylenedithio)tetrathiofulvalene] below 195 K exists an incommensurate modulation [1] and below 125 K a commensurate superstructure with a pronounced distortion of the Ijanions [2], Under ambient pressure the superconducting transition temperature T c is 1.3 K [3] but after a particular pressure-temperature cycling procedure superconductivity can be stabilized at ambient pressure even at r c =8.1 K [4], A recent neutron diffraction study has shown that the high-r c superconducting phase of /?-(BEDT-TTF) 2 I 3 is completely ordered [5] showing that during the pressure-temperature cycling procedure the distortion of the Ij-anions in /?-(BEDT-TTF) 2 I 3 is suppressed resulting in an increase of T c . The IJ-anions and other polyhalide ions used in organic superconductors are sensitive to distortions and slight changes in the crystal.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…In contradiction to the geometry of the Ij-anions in ß-(BEDT-TTF) 2 I 3 below 125 K the (IAuI)"-anions in /?-(BEDT-DDT) 2 IAUI are linear and symmetric in the whole temperature range below 300 K [7]. The structure of /?-(BEDT-TTF) 2 IAuI is completely ordered. However, during the electrochemical process the (IAuI)" can decompose and "impurities" obtained in this way might partially replace (IAuI)"-anions in the crystal lattice [10].…”

Section: Introductionmentioning

confidence: 99%

“…As a consequence the onset temperature for superconductivity varies over a broad temperature range. In this paper we report the Raman-spectra of /?-(BEDT-TTF) 2 IAuIcrystals below and above the temperature of the superconducting transition. Since n-Bu4AuI 2 is used as electrolyte salt in the electrocrystallization of /?-(BEDT-TTF) 2 IAUI the spectra of this compound were also studied.…”

Section: Introductionmentioning

confidence: 99%

“…In this paper we report the Raman-spectra of /?-(BEDT-TTF) 2 IAuIcrystals below and above the temperature of the superconducting transition. Since n-Bu4AuI 2 is used as electrolyte salt in the electrocrystallization of /?-(BEDT-TTF) 2 IAUI the spectra of this compound were also studied. The linear, symmetrical ion (I-Au-I) -has three fundamental modes of vibration: the symmetric stretching mode v t , the asymmetric stretching mode v 2 and a bending mode v 3 .…”

Section: Introductionmentioning

confidence: 99%

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Raman-Studies of the Organic Superconductor β-(BEDT-TTF)₂IAuI

S̀wietlik

Grimm

Schweitzer

et al. 1987

Zeitschrift Für Naturforschung A

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The resonance Raman spectra of (IAuI)--anions in the organic superconductor β-(BEDTTTF)2IAuI as well as in the electrolyte salt n-Bu4AuI2 are investigated. In contrast to β-(BEDT-TTF)2I3 in the crystals of β-BEDT-TTF)2IAuI at low temperature only one Raman line at 120 cm-1 corresponding to the symmetrical stretching mode of the (IAuI)--anion is observed. No distinct change in the Raman spectra is observed at the superconducting transition.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Raman-Studies of the Organic Superconductor β-(BEDT-TTF)₂IAuI

S̀wietlik

Grimm

Schweitzer

et al. 1987

Zeitschrift Für Naturforschung A

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Electrochemically Prepared Radical Salts of BEDT‐TTF: Molecular Metals and Superconductors

Schweitzer

Gogu

Hennig

et al. 1987

Ber Bunsenges Phys Chem

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The structural, electronic and superconducling properties of several electrochemically prepared BEDT -ITF radical salts arc discussed. InlroduclionSince the observation of superconductivity at temperatures up 10 100 K in the metal oxides of the type Ba~La$ _~CUS05(l _ '1 first discovered by Bednarz and Muller [I] superconductivity bas attracted again a lot of interest. A1though the theoretical understanding of .the mechanism leading to superconductivity in these materials is not quite clear yet the most important point is that this discovery has shown that high temperature superconductivity is experimentally achievable.The idea of high temperature superconductivity is quite old. In 1964 Little proposed a model of a metalorganic superconductor at room temperature [2]. His idea has stimulated a lot of interesting developments in the field of lowdimensional conductors. Nevertheless, up to now no high temperature organic superconductor exists. It took a lot of work until 1980 berore superconductivity at 1.3 K under an isotropic pressure of 12 kbar could be observed in an organic material for the first time [3J. At this moment the highest transition temperature into a stable superconducting state at ambient pressure in an organic metal lies at 8 K [4]. The recent finding of higb temperolture superconductivity in the metal oxides will certainly strongly stimulate furtber syntbetic efforts in the search for other organic metals with higher superconducting transition temperatures.On the other hand the understanding of the electronic and superconducting properties of the existing organic metals and especiaUy their relation to the molecular structures of these materials is a prerequisite for further directed developments. The electronic properties of different radical salts obtained from the organic donor bisethyleneditbiolotetrathiafulvalene (BEDT -TIf) by electrochemical methods in tbe presence of II anions [5] are Quite well understood. In addition their crystal structures have been studied over a broad temperature range. The relation of the superconducting properties of these organic metals to their typical crystal structures and especially to small structural cbanges due to phase transitions is known in detail, therefore. In the following a review of the structural, electronic and superconducting properties of the organic metals a-, P-and tXt-{BEDT -TTFhIJ is given.

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Microwave Conductivity in the Pure and Iodine‐Doped Organic Conductor α‐(BEDT‐TTF)₂I₃

Kremer

Helberg

Gogu

et al. 1987

Ber Bunsenges Phys Chem

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The microwave conductivity in dependence of temperature was measured on pure aod iodine doped crystals or a..(BEDT.1TFht) along the stack direction [100] and perpendicular to it [010]. The: uposure times 10 iodine were varied in many step!! between 2 mio and 360 min. The coouctless microwave technique enables to keep tbe same crystal in each case throughout all measurements. -The results show that the microwave conductivity vs. lemperalUre is not influenced distinctly by iodine doping. Only at the onset or the plateau range immediately below the metal·insolator transition at 135 K a small enhancement of the conductivity is round for exposure times larger than 60 min. -In 00 case a transition to a lIupercooductiog state is observed. Thererore recently reported superconductivity may be due to surface effects.

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X-Ray Investigations of the Low-Temperature Phases of the Organic Metals α- and β-(BEDT-TTF)₂I₃

Abstract: The structure of single crystals of the organic metals α- and β-(BEDT-TTF)

Cited by 43 publications

References 1 publication

Raman-Studies of the Organic Superconductor β-(BEDT-TTF)₂IAuI

Raman-Studies of the Organic Superconductor β-(BEDT-TTF)₂IAuI

Electrochemically Prepared Radical Salts of BEDT‐TTF: Molecular Metals and Superconductors

Microwave Conductivity in the Pure and Iodine‐Doped Organic Conductor α‐(BEDT‐TTF)₂I₃

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X-Ray Investigations of the Low-Temperature Phases of the Organic Metals α- and β-(BEDT-TTF)2I3

Abstract: The structure of single crystals of the organic metals α- and β-(BEDT-TTF)

Cited by 43 publications

References 1 publication

Raman-Studies of the Organic Superconductor β-(BEDT-TTF)2IAuI

Raman-Studies of the Organic Superconductor β-(BEDT-TTF)2IAuI

Electrochemically Prepared Radical Salts of BEDT‐TTF: Molecular Metals and Superconductors

Microwave Conductivity in the Pure and Iodine‐Doped Organic Conductor α‐(BEDT‐TTF)2I3

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X-Ray Investigations of the Low-Temperature Phases of the Organic Metals α- and β-(BEDT-TTF)₂I₃

Raman-Studies of the Organic Superconductor β-(BEDT-TTF)₂IAuI

Raman-Studies of the Organic Superconductor β-(BEDT-TTF)₂IAuI

Microwave Conductivity in the Pure and Iodine‐Doped Organic Conductor α‐(BEDT‐TTF)₂I₃